Turn oven down to 350 F.
Meanwhile, heat olive oil in a large skillet over medium heat.
Add red bell pepper, diced onions, and garlic, cook for 3-4 minutes stirring frequently. Remove from skillet and set aside on a plate.
In the same skillet add butter and melt then add the fresh spinach and cook until it is barely wilted, remove any liquid.
In a medium bowl whisk together eggs, milk, salt, pepper, Italian seasoning, mozzarella, and parmesan until well blended.
Layer onion, garlic red bell pepper, and spinach in a greased 9-inch pie plate or quiche dish, using a spatula to spread evenly. Sprinkle chopped tomatoes on top.
Pour egg mixture over the prepared crust using a spatula to spread evenly. You can top with more cheese.
Bake at 350 for 30 minutes or until you can insert a knife in the center and it comes out clean.
Allow cooling for 20 minutes before serving. Enjoy!